Telecommunications equipment produces during operation a significant amount of heat. Therefore, cooling systems are employed to avoid overheating and to keep the involved electrical components within their recommended temperature range of operation such that correct functioning thereof can be guaranteed.
Telecommunications equipment components are typically held in housing structures designed for such purposes, such as racks containing several subracks stapled on top of each other, in which components of equipment, such as cards, can be inserted and secured. An airflow cooling system may be employed to generate an airflow through the rack or subracks that dissipates away the excess heat produced by the telecommunications equipment installed therein. In that case, the air used for cooling has to be previously filtered in order to avoid that dirt suspended in the air is deposited on sensible components of the telecommunications equipment, such as printed circuit boards or sensors. Air filters are used for such purposes.
An air filter is a device typically composed of fibrous materials able to capture solid particles from the air flowing through it such that the airflow is substantially free from such solid particles once it has crossed the filter. In the course of operation of an airflow cooling system for telecommunications equipment, airborne solid particles such as dust, pollen, mould, and bacteria are captured by the filter and accumulate therein. Such solid particles are generally referred to herein as “dirt” or “dirtiness”.
Eventually, the amount of dirt accumulated in the filter is such that the pore structure is occluded and airflow through it is reduced to an extent that proper dissipation of the heat generated by the telecommunications equipment can no longer be guaranteed. Therefore, air filters need to be replaced when such a situation occurs. It is hence useful to monitor the amount of dirt accumulated in the filter, such that the situation can be identified and the replacement of the filter can be initiated in due time.
Commonly known systems for detecting the level of dirtiness of an air filter generally make use of airflow sensors that measure the airflow through the filter or the subrack and signal a decrease thereof below a predefined threshold. However such airflow sensors are technically involved, highly sensible and very costly components. Thus there is room for technical improvements in the detection of the amount of dirt accumulated in a filter mat of an airflow cooling system for telecommunications equipment.